Method of measuring gas barrier property of plastic molding

ABSTRACT

Object of present invention to overcome a problem of a dispersion of an evaluation of gas barrier property depending on absorbed moisture of plastic, and carry out measurements in which a measurement value response is good and accuracy is good, wherein from the beginning of a container the gas barrier property of a plastic molded body does not depend on the amount of moisture absorbed thereof. A method of measuring the gas barrier property of the plastic molded body such as a plastic container, a plastic sheet or a plastic film or the like which uses a gas analyzer to measure the amount of permeation of a measurement object gas permeating through the plastic molded body, comprising: a heat drying process which heats and dries said plastic molded body in a temperature range which does not cause deformation or heat deterioration.

TECHNOLOGICAL FIELD

The present invention is related to a method of measuring a gas barrierproperty which evaluates the gas barrier property of a plastic moldedbody quickly with good accuracy, and is a measuring method adapted forquality control of the gas barrier property when mass producing gasbarrier property plastic containers.

PRIOR ART TECHNOLOGY

A gas barrier property plastic container is disclosed in JapaneseLaid-Open Patent Application No. HEI 8-53116, for example. In JapaneseLaid-Open Patent Application No. HEI 8-53116, with regard to the oxygenbarrier property of a plastic container, the oxygen permeability wasmeasured at 40° C. using an OX-TRANTWIN manufactured by Modern ControlCompany. Further, with regard to the carbon dioxide gas barrierproperty, the carbon dioxide gas permeability was measured at 25° C.using a PERMATRANC-4 Model manufactured by Modern Control Company.

The gas barrier property measurement of a plastic molded body such as aplastic container, a plastic sheet or a plastic film or the like mainlyuses the method disclosed in Japanese Laid-Open Patent Application No.HEI 8-53116. In the case of a plastic container, because the thicknessis thick and the shape of the container is complex, a period of aboutone week is required until the measurement value stabilizes.Accordingly, up to now there has not been a method which makes itpossible to quickly evaluate the gas barrier property.

Further, Japanese Laid-Open Patent Application No. HEI 11-118763discloses technology for a method of measuring hydrogen gasconcentration, for example, as an invention which measures gasconcentration with high accuracy by atmospheric pressure ionization massspectrometry.

In the technology of Japanese Laid-Open Patent Application No. HEI11-118763, instead of measuring hydrogen directly, water (water vapor)is created from hydrogen, and then by measuring this water, a hydrogenconcentration conversion is obtained. As described in line 10 of theright column on page 2 of the specification of Japanese Laid-Open PatentApplication No. HEI 11-118763, the reason water is created is because ofthe special problems that arise in mass spectrometry due to the factthat hydrogen does not ionize efficiently into a parent ion (H₂+, mass2).

A test which evaluates the gas barrier property using an atmosphericpressure ionization mass spectrometer (APIMS) has not been developedyet.

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

As described in Japanese Laid-Open Patent Application No. HEI 8-53116, agas permeability measuring device measures oxygen or carbon dioxideseparately. In the experience of the present inventors, the time ittakes to measure the gas permeability using the apparatus disclosed inJapanese Laid-Open Patent Application No. HEI 8-53116 requires at leastone week for the measurement value to stabilize in the case where theoxygen permeability is measured, for example. Accordingly, if theaccuracy of the measurement value is to be made higher, a period of timegreater than one week becomes necessary in order to measure the gasbarrier property of one plastic container. For the reason that a longperiod of time is required for measurement in this way, the presentinventors assumed that in Japanese Laid-Open Patent Application No. HEI8-53116, from the viewpoint of securing measurement accuracy, becausethe flow rate of the carrier gas which carries the permeated measurementobject gas can not be made larger, a long period of time is required dueto the fact that the circulation of gas inside the container is poor andthe response of the measurement value is slow.

Further, there are plastic resins that have a large hygroscopicitydepending on the type, for example, and the resin of polyethyleneterephthalate (PET) containers has a large hygroscopicity, wherein 100 gof resin absorbs 0.3˜0.5 g of water at 20° C. at a relative humidity of60˜80%. The present inventors discovered that there are effects on thedetector when water molecules absorbed inside the resin are present, andthe measurement value of the oxygen permeability had large variationsdepending on the water content of the resin.

After plastic containers are formed, in the case where the containersare stored in a warehouse, the containers will absorb moisture. In thecase where quality confirmation of the gas barrier property is carriedout in a plastic container forming plant after a period of time haspassed since the containers were formed, and in the case where the gasbarrier property of the plastic containers forms one qualityconfirmation subject when a beverage bottling plant receives the plasticcontainers, the detector receives effects depending on the difference ofthe amount of absorbed moisture, whereby the evaluation of the gasbarrier property becomes dispersed.

It is an object of the present invention to overcome the problem of thedispersion of the evaluation of the gas barrier property depending onthe absorbed moisture of plastic described above, and carry outmeasurements in which the measurement value response is good andaccuracy is good, wherein from the beginning of the container the gasbarrier property of the plastic molded body does not depend on theamount of moisture absorbed thereof.

Namely, it is an object of the present invention to provide a method ofmeasuring a gas barrier property which improves the accuracy of gasbarrier property measurements by heating a plastic molded body in atemperature range which does not cause deformation or heat deteriorationto dry the plastic molded body before measuring a measurement object gaspermeated through the plastic molded body, wherein preferably theabsorbed water is removed by heat drying, and the accuracy of gasbarrier property measurements is improved by quickly adjusting theplastic molded body for which the effects of water have been eliminated.Further, this provides a method of measuring a gas barrier propertywhich makes the detection of the amount of permeation of the measurementobject gas respond with good response and high accuracy and drasticallyshortens the measurement time by using a mass spectrometer, inparticular an atmospheric pressure ionization mass spectrometer, andflowing a relatively large amount of carrier gas. At this time, it is anobject to measure not just one measurement object gas, but a pluralityof measurement object gases simultaneously with good accuracy.

Further, it is an object of the present invention to provide a method ofmeasuring a gas barrier property of a plastic molded body, in particulara plastic container or a gas barrier property plastic container whereinone of the inner surface or the outer surface or both surfaces thereofare coated with a gas barrier property thin film.

It is an object of the present invention to provide a method ofmeasuring the oxygen gas barrier property of a plastic molded body, andin particular a method of measuring the oxygen gas barrier propertydepending on permeation of oxygen from an air atmosphere.

It is an object of the present invention to provide a method which canmeasure the gas barrier property of one of oxygen gas, carbon dioxidegas or hydrogen gas or a combination thereof with good accuracy whileeliminating the effects of impurity gases by creating an atmospherecontaining a measurement object gas from a reference gas of measurementobject gas-argon or a reference gas of measurement object gas-nitrogengas which is adjusted so that the measurement object gas forms aprescribed pressure, wherein the measurement object gas is one of oxygengas, carbon dioxide gas or hydrogen gas or a combination thereof.

Further, it is an object of the present invention to provide a method ofmeasuring gas barrier property which completely eliminates the effectsof oxygen gas present inside the plastic resin before measurement byusing oxygen gas of mass number 18 as the measurement object gas, andseparately measuring the oxygen gas (oxygen gas of mass number 16 is99.762%, oxygen gas of mass number 17 is 0.038%, and oxygen gas of massnumber 18 is 0.200%, wherein oxygen gas of mass number 16 forms themajor portion) present inside the plastic resin before measurement andthe oxygen gas permeating through the plastic resin at the time ofmeasurement. Inside the plastic resin, permeation occurs due to diffusepermeation depending on the concentration gradient of the gas, but theinitial data of a normal measuring method detects as a measurement valueboth the oxygen gas present inside the plastic resin before measurementand the oxygen gas permeating by diffuse permeation. In the presentinvention, it can be expected that the true measurement value of the gasbarrier property is quickly detected by detecting only the oxygen gaspermeating by diffuse permeation from the beginning of measurement.

Further, it is an object of the present invention to provide a measuringmethod which combines at least one gas from oxygen gas of mass number16, carbon dioxide gas or hydrogen gas with oxygen gas of mass number 18to form measurement object gases, and can carry out simultaneousmeasurements of the gas barrier property of a plurality of gas types.

In the case where a gas barrier property plastic container is massproduced, instead of corresponding to only one coating chamber forcoating the container with a gas barrier property thin film, the realityis that a plurality of chambers are operated simultaneously or areoperated alternately in sequence. In this regard, it is another objectof the present invention to provide a method of measuring a gas barrierproperty which evaluates the gas barrier property of each container whenplastic containers are coated with gas barrier property thin films in amass production state using a plurality of coating chambers, andunderstands the operating state of the coating chambers by comparing thegas barrier properties of the containers which underwent film formationin each coating chamber. This is because there are many cases where thequality of the gas barrier thin film created by film formation dependson whether or not the coating chamber is operating normally. Inparticular, because the present invention can quickly measure the gasbarrier property, it is expected that it is possible to judge thequality evaluation of the gas barrier properties of containers on aproduction line by the result of the present measuring method. The priorart measuring method which requires an evaluation time of one week ormore takes too much time as an evaluating method in a production line.

It is an object of the present invention to quickly carry out gassubstitution to quickly reach a steady state which makes it possible tobegin measurements by setting the flow rate of argon gas or nitrogen gassupplied to an argon gas atmosphere side or a nitrogen gas atmosphereside at or above a prescribed rate in an atmosphere adjusting processand a measurement object gas measuring process.

Means for Solving the Problems

In view of the problems described above, through diligent development todesign higher measurement accuracy by controlling the dispersion ofmeasurement data due to water molecules and design high speedmeasurements by efficiently carrying out gas substitution required formeasurements for a plastic molded body, the present inventors achievedthe present invention by discovering that the problems described aboveare solved efficiently by (1) heat drying the plastic molded body beforemeasuring the gas permeability, and (2) preferably using a massspectrometer, in particular an atmospheric pressure ionization massspectrometer even though it is possible to achieve a higher accuracy anda higher speed using various gas measuring methods if heat drying of theplastic molded body is made a precondition.

Namely, the method of measuring the gas barrier property of a plasticmolded body according to the present invention is a method of measuringthe gas barrier property of a plastic molded body such as a plasticcontainer, a plastic sheet or a plastic film or the like which uses agas analyzer to measure the amount of permeation of a measurement objectgas permeating through the plastic molded body, and includes a heatdrying process which heats and dries said plastic molded body in atemperature range which does not cause deformation or heatdeterioration. The method of measuring the gas barrier property of aplastic molded body according to the present invention includes the casewhere such method includes an atmosphere adjusting process which formsan atmosphere including a measurement object gas at one side of the wallsurfaces of said plastic molded body, and forms a carrier gas atmospherewhich carries said measurement object gas after permeation to said gasanalyzer at the other side forming a front and back relationship of saidwall surfaces. In this regard, the carrier gas atmosphere is preferablyan argon atmosphere or a nitrogen gas atmosphere. In this regard, inorder to shorten the period of time required for measurements, said heatdrying process is preferably carried out at the same time in saidatmosphere adjusting process. Further, the method of measuring the gasbarrier property of a plastic molded body according to the presentinvention includes the case where such method includes a measurementobject gas measuring process which measures the amount of permeation ofsaid measurement object gas permeating through said plastic molded bodyfrom one side of said wall surfaces toward the other side with said gasanalyzer at the time when said amount of permeation of said measurementobject gas reaches a roughly steady state.

In the method of measuring the gas barrier property of a plastic moldedbody according to the present invention, said heat drying processincludes a process which removes water absorbed by said plastic moldedbody. Further, said heat drying process includes a process whichsubstitutes adsorption gas adsorbed on one side of the wall surfaces ofsaid plastic molded body with gas of the atmosphere including saidmeasurement object gas, and substitutes adsorption gas adsorbed on theother side forming a front and back relationship of the wall surfaces ofsaid plastic molded body with gas of said carrier gas atmosphere.

Further, in the method of measuring the gas barrier property of aplastic molded body according to the present invention, the gas analyzeris preferably a mass spectrometer, and more preferably an atmosphericpressure ionization mass spectrometer.

In the method of measuring the gas barrier property of a plastic moldedbody according to the present invention, when said plastic molded bodyis a plastic container or a gas barrier property plastic container inwhich a gas barrier property thin film is coated on one of the innersurface or the outer surface or both surfaces thereof, preferably anatmosphere including a measurement object gas is formed outside thecontainer and said carrier gas atmosphere is formed inside the containerin said atmosphere adjusting process.

In this regard, in the method of measuring the gas barrier property of aplastic molded body according to the present invention, preferably saidmeasurement object gas is oxygen gas, and the atmosphere including saidmeasurement object gas is an air atmosphere.

Alternatively, preferably said measurement object gas is one of oxygengas, carbon dioxide gas or hydrogen gas or a combination thereof, andthe atmosphere including said measurement object gas is a measurementobject gas-argon atmosphere or a measurement object gas-nitrogen gasatmosphere in which adjustments are carried out so that said measurementobject gas forms a prescribed partial pressure.

Alternatively, preferably the measurement object gas is oxygen gas ofmass number 18, and the atmosphere including said measurement object gasis an oxygen gas of mass number 18—argon atmosphere or an oxygen gas ofmass number 18—nitrogen gas atmosphere in which adjustments are carriedout so the oxygen gas of mass number 18 forms a prescribed partialpressure.

Alternatively, preferably the measurement object gas is a mixed gas ofoxygen gas of mass number 18 and at least one gas from oxygen gas ofmass number 16, carbon dioxide gas or hydrogen gas, and the atmosphereincluding said measurement object gas is a measurement object gas-argonatmosphere or a measurement object gas-nitrogen gas atmosphere in whichadjustments are carried out so that said measurement object gas forms aprescribed partial pressure.

Further, in the method of measuring the gas barrier property of aplastic molded body according to the present invention, preferably saidplastic container is a gas barrier property plastic container which ismass produced by arranging a plurality of coating chambers for coatingthe inner surface or the outer surface of the plastic container or bothsurfaces thereof with a gas barrier property thin film and operatingsaid coating chambers simultaneously or sequentially, said heat dryingprocess, said atmosphere adjusting process and said measurement objectgas measuring process are carried out at a level where a prescribednumber of film formations is carried out in each of said coatingchambers, and then a chamber operation judgment process which judgespoor operation of said coating chambers by comparing the gas barrierproperties of said gas barrier property plastic containers in each ofsaid coating chambers is carried out.

Further, in the method of measuring the gas barrier property of aplastic molded body according to the present invention, preferably theargon flow rate per 1 minute or the nitrogen flow rate per 1 minutesupplied to said carrier gas atmosphere side is greater than or equal totwice the volume of said plastic container in said atmosphere adjustingprocess and said measurement object gas measuring process.

Effect of the Invention

The present invention makes it possible to overcome the problem of thedispersion of the evaluation of the gas barrier property depending onthe absorbed moisture of plastic described above, and carry outmeasurements in which the measurement value response is good andaccuracy is good, wherein from the beginning of the container the gasbarrier property of the plastic molded body does not depend on theamount of moisture absorbed thereof. Namely, the accuracy of gas barrierproperty measurements can be improved by quickly adjusting the plasticmolded body for which the effects of water have been eliminated.Further, it was possible to provide a method of measuring a gas barrierproperty which makes the detection of the amount of permeation of themeasurement object gas respond with good response and high accuracy anddrastically shortens the measurement time by preferably using a massspectrometer, and more preferably an atmospheric pressure ionizationmass spectrometer as the gas analyzer, and flowing a relatively largeamount of carrier gas. Further, evaluation was possible in several hourseven in a plastic molded body having a complex shape such as a plasticcontainer or a gas barrier property plastic container wherein one of theinner surface or the outer surface or both surfaces thereof are coatedwith a gas barrier property thin film. At this time, it was possible tomeasure not just one measurement object gas, but a plurality ofmeasurement object gases simultaneously with good accuracy. Themeasurement object gas is oxygen gas, carbon dioxide gas, hydrogen gasand a combination of these. Further, by using oxygen gas of mass number18 as the measurement object gas, it was possible to provide a gasbarrier property measuring method which completely eliminates theeffects of oxygen gas present inside the plastic resin beforemeasurements. Further, it was possible to provide a method of measuringa gas barrier property which evaluates the gas barrier property of eachcontainer when plastic containers are coated with gas barrier propertythin films in a mass production state using a plurality of coatingchambers, and understands the operating state of the coating chambers bycomparing the gas barrier properties of the containers which underwentfilm formation in each coating chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual structure drawing showing one embodiment of acoating apparatus of a mass production machine.

FIG. 2 is a conceptual drawing showing one embodiment of a coatingchamber arrangement of a coating apparatus.

FIG. 3 is a schematic drawing showing one embodiment of an apparatuswhich measures the gas barrier property of a plastic container.

FIG. 4 is a graph which shows the changes in oxygen gas concentrationand hydrogen gas concentration depending on the measurement elapsed timefor Specific Examples 1 and 2.

FIG. 5 is a graph which shows the relationship between the ionicstrength and the mass number at the time of the background measurementof the operating procedure (1) of the gas barrier property measuringmethod in Specific Examples 1 and 2.

FIG. 6 is a graph which shows the relationship between the ionicstrength and the mass number at the time of the oxygen gas concentrationmeasurement of Specific Example 1.

FIG. 7 is a graph which shows the relationship between the ionicstrength and the mass number at the time of the hydrogen gasconcentration measurement of Specific Example 2.

FIG. 8 is a graph which shows the changes in oxygen gas concentrationand hydrogen gas concentration depending on the measurement elapsed timefor Specific Examples 3 and 4.

FIG. 9 is a graph which shows the relationship between the ionicstrength and the mass number at the time of the background measurementof the operating procedure (1) of the gas barrier property measuringmethod in Specific Examples 3 and 4.

FIG. 10 is a graph which shows the relationship between the ionicstrength and the mass number at the time of the oxygen gas concentrationmeasurement of Specific Example 3.

FIG. 11 is a graph which shows the relationship between the ionicstrength and the mass number at the time of the hydrogen gasconcentration measurement of Specific Example 4.

FIG. 12 is a graph which shows the relationship between the filmthickness of the DLC film and the amount of oxygen gas permeation.

FIG. 13 is a graph which shows the relationship between the filmthickness of the DLC film and the amount of hydrogen gas permeation.

FIG. 14 is a graph which shows the relationship between the measurementday number and the amount of oxygen gas permeation at such times forComparative Examples 4˜8.

FIG. 15 is a graph showing the change in oxygen concentration inside thecarrier gas flowing through the inside of a PET container, and shows thecase where there is a heat drying process and the case where there isnone.

FIG. 16 is a graph showing the change in oxygen concentration inside thecarrier gas flowing through the inside of a polyethylene container, andshows the case where there is a heat drying process and the case wherethere is none.

The meaning of the symbols is as follows. 1 is a liquid argon tank, 2 isa liquid argon vaporizer, 3, 22 are pressure reducing valves, 4 is agetter, 5 is a bypass line, 6, 9, 23 are mass flow controllers, 7, 10,14 are purifiers, 8 is a PET bottle line, 11 is a PET bottle, 12 isvalve B, 13 is valve A, 15 is an APIMS, 16 is a gas supply pipeline, 17is a gas exhaust pipeline, 21 is a standard gas cylinder, 24 is PETbottle sealing means, and 31 is PET bottle outside atmosphere adjustingmeans.

PREFERRED EMBODIMENTS OF THE INVENTION

Detailed descriptions showing embodiments and specific examples of thepresent invention are given below, but it should not be interpreted thatthe present invention is limited to these descriptions.

The plastic molded body according to the present invention can beillustrated by a plastic container, a plastic sheet or a plastic film.In the present embodiment, a description is given for the example of aplastic container, in particular a beverage container. In the case wherethe gas barrier property of a film thickness of several tens of μm ismeasured for a plastic film, because the film thickness is thin, thereare instances where the measurement is completed in a relatively shortperiod of time. In the case where a plastic container forms themeasurement object, because the resin thickness is 0.3˜1 mm, a quickmeasurement is required compared with the case of a film. Further,because a beverage container has a three-dimensional shape with acomplicated shape inside the container, a long period of time isrequired to flow the carrier gas and carry out gas substitutioncompletely. Accordingly, it is an object for which it is difficult toevaluate the gas barrier property at high speed and high accuracy. Thepresent invention is not influenced by the shape of the container, andthe use of the container can be illustrated by carbonated beverages suchas beer and the like, fruit juices, nutrient drinks, and medicines.

The resin used when forming the plastic container of the presentinvention can be illustrated by polyethylene terephthalate (PET) resin,polyethylene terephthalate type co-polyester resin (a copolymer namedPETG which uses cyclohexane dimethanol in place of ethylene glycol forthe alcohol component of polyester, made by Eastman Chemical),polybutylene terephthalate resin, polyethylene naphthalate resin,polyethylene (PE) resin, polypropylene (PP) resin, cycloolefin copolymer(COC, cyclic olefin copolymer) resin, ionomer resin,poly-4-methylpentene-1 resin, polymethyl methacrylate resin, polystyrene(PS) resin, ethylene-vinyl alcohol copolymer resin, polyacrylonitrileresin, polyvinyl chloride resin, polyvinylidene chloride (PVDC) resin,polyamide resin, polyamide-imide resin, polyacetal resin, polycarbonate(PC) resin, polysulfone resin, or ethylene tetrafluoride resin,acrylonitrile-styrene resin, polyether sulfone resin, andacrylonitrile-butadiene-styrene resin. Of these, PET is particularlypreferred. In the present invention, a description is given for a PETbottle as an example of a plastic container.

The percentage of water absorption of the plastic (24 hours, 23° C.) isdivided into three classifications.

-   -   (1) Material which is difficult to absorb moisture, PE: <0.01%,        PP: <0.005%, PS: 0.04˜0.06%, PVDC: trace.    -   (2) Intermediate material, PET: 0.3˜0.5%, PC: 0.35%, polyether        sulfone: 0.3˜0.4%.    -   (3) Material having high moisture absorbance, polyimide: 2.9%,        nylon 6: 9.5%, cellulose acetate: 5˜9%.

The plastic molded body according to the present invention may be a gasbarrier property plastic container wherein one of the inner surface orthe outer surface or both surfaces thereof are coated with a gas barrierproperty thin film. The gas barrier property thin film which coats thewall surfaces of the plastic container can be illustrated by SiOx, DLC(diamond like carbon), DLC containing Si, polymer like carbon, aluminumoxide, polymer like silicon nitride, and acrylic acid resin coating. Ofthese, DLC is particularly preferred because it has a superior oxygenbarrier property and water vapor barrier property, is chemicallyinactive, can be disposed in the same way as plastic because carbon andhydrogen form the main components, and has the ability to follow theexpansion and contraction of plastic because it is flexible. In thepresent invention, the DLC film is a film called an i-carbon film or ahydrogenated amorphous carbon film (a-C:H), and also includes a hardcarbon film. Further, a DLC film is an amorphous state carbon film, andincludes SP³ bonding. A hydrocarbon gas such as acetylene, for example,is used as a source gas for forming the DLC film, and a Si-containinghydrocarbon gas is used as a source gas for forming a Si-containing DLCfilm. By forming this kind of DLC film on one of the inner surface orthe outer surface of the container or on both surfaces thereof, acontainer is obtained which can be used as a one-way container or areturnable container for carbonated beverages and sparkling beveragesand the like.

Further, the gas barrier property thin film can be coated on the innersurface or the outer surface or both thereof, but the forming of a gasbarrier property thin film on the inner surface is preferred in view ofsecuring a gas barrier property and preventing either the contents frombeing absorbed into the plastic or minute quantities of componentscontained inside the plastic from dissolving into the contents and thefact that it is economical. Further, as for the method of forming a DLCfilm, there is the film forming method described in Laid-Open PatentApplication No. HEI 8-53116, for example.

The method of measuring a gas barrier property of a plastic molded bodyaccording to the present invention is a method which carries outmeasurements of the amount of permeation of a measurement object gaspermeating through the plastic molded body with a gas analyzer, whichincludes at least (1) a heat drying process which heats and dries theplastic molded body in a temperature range which does not causedeformation or heat deterioration. This heat drying process may includea process which removes water absorbed by the plastic molded body.Further, the heat drying process may include a process which substitutesthe adsorption gas adsorbed on one side of the wall surfaces of theplastic molded body with a gas atmosphere containing a measurementobject gas, and substitutes the adsorption gas adsorbed on the otherside forming a front and back relationship of the wall surfaces of theplastic molded body with a gas of a carrier gas atmosphere such asargon, nitrogen gas or the like.

The method of measuring a gas barrier property of a plastic molded bodyaccording to the present invention is a method further includes (2) anatmosphere adjusting process which forms an atmosphere including ameasurement object gas at one side of the wall surfaces of the plasticmolded body, and forms a carrier gas atmosphere such as argon, nitrogengas or the like on the other side forming a front and back relationshipof the wall surfaces. This carrier gas is a gas which carries saidmeasurement object gas after permeation to said gas analyzer, and maycontain 0.5˜3.0% hydrogen gas for removing oxygen as impurities. Thehydrogen gas for removing oxygen as impurities reacts by catalyzingoxygen as impurities inside the carrier gas before making contact withthe plastic molded body. On the other hand, because there is no reactionwith oxygen after contact with the catalyst, there is no reaction withpermeated oxygen.

The method of measuring a gas barrier property of a plastic molded bodyaccording to the present invention is a method further includes (3) ameasurement object gas measuring process which measures the amount ofpermeation with various gas analyzers, preferably a mass spectrometer,and more preferably an atmospheric pressure ionization mass spectrometerwhen the measurement object gas permeates through the plastic moldedbody from one side of the wall surfaces to the other side and the amountof the permeated measurement object gas forms a roughly steady state,namely when the detector value of the concentration of the measurementobject gas reaches a prescribed value.

The present inventors discovered that when water molecules due toabsorbed moisture and the like forming a measurement object are presentinside the molecular structure of the plastic molded body, the watermolecules will have effects on the detector, and this will cause themeasurement value of oxygen, carbon dioxide and the like to becomeunstable, but on the other hand it is possible to eliminate the adverseeffects of water molecules by removing the water molecules absorbed inthe plastic molded body. For example, PET resin absorbs 0.3˜0.5 g ofwater per 100 g. In the case where a beverage bottling plant or the likereceives plastic containers that have been coated with a gas barrierproperty thin film, it is normal procedure to carry out a qualityinspection of whether or not the containers have prescribed gas barrierproperties. In this regard, there are many cases where moistureabsorption occurs in a gas barrier property thin film coated plasticcontainer. If a measurement of the gas barrier property of thiscontainer is carried out as is, a measurement error will be includeddepending on the moisture absorption state of the container. In thepresent invention, preferably a heat drying process is provided beforemeasuring the gas barrier property. The heat drying process is carriedout for the purpose of removing water molecules absorbed in the plasticmolded body, eliminating the adverse effects of water molecules on thedetector, and reducing the effect of adsorption gas adsorbed on thesurface of the plastic molded body. Further, as means for removing thewater molecules absorbed in the plastic molded body, means whichcontinuously flow large quantities of dry argon gas or dry nitrogen gasthrough the plastic molded body have been conceived. However, becausethe diffusion rate of water molecules depends on the temperature, it isunderstood that about one week is required to remove most of the watermolecules from the resin. In comparison with this, the removal of watermolecules can be carried out at high speed by heat drying. At this time,preferably gas substitution with dry argon or dry nitrogen gas iscontinuously carried out inside the plastic container at the same timeheat drying is carried out. This is not for the purpose of drying theresin with dry argon or dry nitrogen gas, but is instead for the purposeof carry out exhaust with dry argon or dry nitrogen gas as a carrier gasfor the water molecules that diffuse and are released from the inside ofthe resin to the outside of the resin, and for this reason there is noneed to flow a large quantity of dry argon or dry nitrogen gas. Further,the APIMS which is the detector used in the present invention requires aheat drying process because it is easy to receive effects from watermolecules.

In the heat drying process, the plastic molded body is heated in atemperature range which does not cause deformation or heatdeterioration. Blowing hot gas of dry argon or dry nitrogen gas in thecontainer is effective for carrying out quick drying, but when heatingis carried out at a high temperature above the vicinity of the glasstransition point, the container will shrink and create deformations.Accordingly, in the present invention, preferably drying is carried outat or below a temperature level where shape deterioration and thin filmdeterioration such as peeling, cracking and like of the gas barrierproperty thin film do not occur. For example, for a PET bottle,preferably heating is carried out at 60˜80° C.

The atmosphere adjusting process provides a difference in concentrationof measurement object gas on the front surface and the back surface nearthe wall surfaces in a front and back relationship of the plastic moldedbody, and this is provided to carry out diffusion of gas from the highconcentration side to the low concentration side. In this regard, in theatmosphere adjusting process, the heat drying process may be carried outat the same time. The atmosphere adjusting process requires a littletime until stabilizing, and the heat drying process requires a littletime for heating and cooling, but these can be carried out at the sametime, and this leads to a shortening of the time required formeasurements.

When taking a plastic container as an example, preferably the outside ofthe plastic container forms an atmosphere containing a measurementobject gas, and the inside of the container forms a carrier gasatmosphere such as an argon atmosphere or a nitrogen gas atmosphere. Inthis case, the measurement object gas concentration outside thecontainer is a high concentration, the measurement object gasconcentration inside the container forms a low concentration, and themeasurement object gas diffuses and permeates through the inside of theresin from the outer surface of the container toward the inner surfaceof the container. Further, the plastic container may be a gas barrierproperty plastic container wherein one of the inner surface or the outersurface or both surfaces thereof are coated with a gas barrier propertythin film.

In one embodiment which measures the oxygen gas barrier property, oxygengas forms the measurement object gas, and an air atmosphere forms theatmosphere containing the measurement object gas. In order to carry thepermeated oxygen gas to the detector, argon gas or nitrogen gas isflowed as a carrier gas at a flow rate of 500˜2000 ml/min, for example.Argon gas or nitrogen gas forms a substitution gas until a steady stateis formed.

In the present embodiment, because a lowering of the measurementaccuracy is brought about when water molecules are present in themeasurement path, preferably water molecules are removed as much aspossible. Namely, preferably high purity argon or high purity nitrogengas is used as a carrier gas, and a purifier is provided directly afterthe argon supply source or the nitrogen gas supply source to removewater molecules.

In an embodiment in which the oxygen gas barrier property, the carbondioxide gas barrier property or the hydrogen gas barrier property ismeasured separately or these are combined to measure the gas barrierproperty at the same time, the measurement object gas is formed by oneof oxygen gas, carbon dioxide gas, or hydrogen gas or a combination ofthese. Then, the atmosphere containing the measurement object gas isformed by a measurement object gas-argon atmosphere or a measurementobject gas-nitrogen gas atmosphere in which the measurement object gasis adjusted to form a prescribed partial pressure. In this case, inorder to create a measurement object gas-argon atmosphere, oxygengas-argon gas, carbon dioxide gas-argon gas, hydrogen gas-argon gas,oxygen gas-carbon dioxide gas-argon gas, oxygen gas-hydrogen gas-argongas, hydrogen gas-carbon dioxide gas-argon gas, or oxygen gas-carbondioxide gas-hydrogen gas-argon gas is prepared as a standard gas byadjusting each gas to have a prescribe partial pressure, and then thisstandard gas is flowed through the gas path. Alternatively, in order tocreate a measurement object gas-nitrogen gas atmosphere, oxygengas-nitrogen gas, carbon dioxide gas-nitrogen gas, hydrogen gas-nitrogengas, oxygen gas-carbon dioxide gas-nitrogen gas, oxygen gas-hydrogengas-nitrogen gas, hydrogen gas-carbon dioxide gas-nitrogen gas, oroxygen gas-carbon dioxide gas-hydrogen gas-nitrogen gas is prepared as astandard gas by adjusting each gas to have a prescribe partial pressure,and then this standard gas is flowed through the gas path. Compared withthe case where the atmosphere containing the measurement object gas isformed by an air atmosphere at the time the gas barrier property ofoxygen gas is measured, because the effects of impurity gases such aswater vapor in particular are eliminated, an improvement of measurementaccuracy can be expected.

In another embodiment which measures the oxygen gas barrier property,the measurement object gas is formed by oxygen gas of mass number 18,and the atmosphere containing the measurement object gas is formed by anoxygen gas of mass number 18-argon atmosphere in which the oxygen gas ofmass number 18 is adjusted to form a prescribed partial pressure or isformed by an oxygen gas of mass number 18-nitrogen gas atmosphere inwhich the oxygen gas of mass number 18 is adjusted to form a prescribedpartial pressure. The reason for using oxygen gas of mass number 18 isas follows. Normal oxygen gas is mass number 16, and APIMS which is thedetector of atmospheric pressure ionization spectrometry can detect thedifference in mass number. On the other hand, molecular properties suchas gas permeation and the like are the same because they are the sameelement. Because the proportion of oxygen gas of mass number 18 presentinside the plastic resin from the beginning is extremely small at0.200%, it is possible to separate the detection error due to diffusepermeation of oxygen gas (mass number 16) present inside the plasticresin from the beginning by measuring oxygen gas of mass number 18 as ameasurement object gas. Namely, if oxygen gas of mass number 18 ismeasured, the state where permeation through the plastic molded bodybegins is understood in real time.

In the applied embodiment of the case where oxygen gas of mass number 18is used as a measurement object gas, a measurement object gas is formedby combining at least one gas of oxygen gas of mass number 16, carbondioxide gas or hydrogen gas with oxygen gas of mass number 18, and asfor the atmosphere containing the measurement object gas, a standard gasof a measurement object gas-argon atmosphere in which the measurementobject gas is adjusted to form a prescribed partial pressure, or astandard gas of a measurement object gas-nitrogen gas atmosphere inwhich the measurement object gas is adjusted to form a prescribedpartial pressure is prepared and such atmosphere is created. In thiscase, in addition to making it possible to separate the detection errordue to diffuse permeation of the oxygen gas (mass number 16) presentinside the plastic resin from the beginning, it becomes possible tocarry out simultaneous analysis of carbon dioxide gas, oxygen gas,hydrogen gas or a combination of these gases. By using a standard gas,it is possible to eliminate the effects of impurity gases.

The composition of the standard gases of measurement object gas-argongas and the composition of the standard gases of measurement objectgas-nitrogen gas are shown in Table 1. TABLE 1 Concentration of StandardConcentration of Oxygen Gas of Concentration of Concentration of GasOxygen Gas of Mass Mass Number 18 Carbon Dioxide Hydrogen Gas NumberNumber 16 (%) (%) Gas (%) (%) Concentration of Argon (%) 1 21 79 2 21 793 4 94 4 4 94 5 21 3 1 75 6 21 3 76 7 21 1 78 8 3 1 96 9 21 1 3 1 74 1021 3 1 75 11 21 1 78 12 21 3 76 13 21 1 78 14 21 1 3 75 Concentration ofNitrogen Gas (%) 15 21 79 16 21 79 17 4 94 18 4 94 19 21 3 1 75 20 21 376 21 21 1 78 22 3 1 96 23 21 1 3 1 74 24 21 3 1 75 25 21 1 78 26 21 376 27 21 1 78 28 21 1 3 75

In the measurement object gas measuring process, the measurement objectgas permeates through the plastic molded body from one side of the wallsurfaces toward the other side, the permeated measurement object gas iscarried to the gas detector with argon gas or nitrogen gas as a carriergas, and the amount of permeation of the measurement object gas isdetermined by measuring the gas concentration of the measurement objectgas at the time when the detected amount of permeation of themeasurement object gas reaches a steady state. For example, in the casewhere a plastic container forms a measurement object, the outside of thecontainer forms an atmosphere which includes a measurement object gas ata prescribed partial pressure. On the other hand, because the permeatedmeasurement object gas is carried sequentially to the detector withargon gas or nitrogen gas as a carrier gas, the measurement object gasconcentration (partial pressure) inside the container is close toroughly zero.

In this regard, the gas permeability coefficient P of plastic is shownby Equation 1 using the gas diffusion coefficient D inside the plasticand the gas solubility coefficient S to the plastic.P=D×S  Equation 1

The gas permeation amount Q of the plastic is shown by Equation 2 usingthe gas permeability coefficient P, the permeation area A, thepermeation time t and the pressure p.Q=P×A×t×p  Equation 2

The gas permeation amount Q of the plastic can be represented byEquation 2, but in actual measurements if the concentration gradientbetween the measurement object gas concentration (which is a prescribedconcentration) outside the plastic container and the measurement objectgas concentration (the measurement object gas concentration is roughlyzero as described above) inside the plastic container does not reach asteady state, measurement errors will occur. Gas molecules diffuseinside the plastic, and the time it takes for the concentration gradientof the gas molecules inside the plastic to reach a steady state iscalled the “lag time”. As shown in Equation 3, the lag time isproportional to the square of the plastic thickness, and is inverselyproportional to the diffusion coefficient.Lag Time=(Plastic Thickness)²/(6×Diffusion Coefficient D)  Equation 3

In this regard, Table 2 shows the data shown in Non-Patent Document 1.TABLE 2 Gas P D S Ep E_(D) σ² σ⁻² N₂ 1 1 1 1 1 1 1 CO 1.2 1.1 1.1 1 10.95 1.05 CH₄ 3.4 0.7 4.9 (1) (1) 0.98 1.02 O₂ 3.8 1.7 2.2 0.86 0.900.83 1.2 He 15 60 0.25 0.62 0.45 0.45 2.2 H₂ 22.5 30 0.75 0.70 0.65 0.551.8 CO₂ 24 1 24 0.75 1.03 1.0 1 H₂O (550) 5 — 0.75 0.75 0.94 1.06(Note)Other Gases are converted using 1 for Nitrogen.(Non-Patent Document 1) D. W. Van Krevelen, Properties of Polymers, P555

As is clear from Equation 3, the diffusion coefficient D is differentand the lag time is also different depending on the type of measurementobject gas, but when reaching the time where each of the measurementobject gases undergoing diffuse permeation inside the resin finishespermeating, the permeation of the measurement object gases can be saidto have formed a steady state. However, there are also instances wherethe plastic molded body has a complicated shape, and because thepermeation needs to reach a steady state in all parts, preferably thegas permeation is judged to have reached a steady state after aprescribed period of time has elapsed from the detection of permeationof a measurement object gas. Further, even in the state where permeationbecomes steady in each part of the container, the measurement object gasremains inside the container until being carried to the detector. Thegas inside the container (in this case, a carrier gas such as argon gasor nitrogen gas with the measurement object gas) reaches a fixedconcentration, and after the effect of this remaining gas is eliminated,a steady state is finally reached. Accordingly, until the amount ofpermeation of the measurement object gas reaches a steady state, thepermeation of the measurement object gas must reach a steady state andthe gas concentration inside the container must become fixed.

The detection of the measurement object gas is carried out with a gasanalyzer. Preferably, this is carried out by a non-deflection type massspectrometer such as a quadrupole type mass spectrometer or atime-of-flight mass spectrometer or the like, or a deflection type massspectrometer such as a magnetic deflection type mass spectrometer, atrochoid type mass spectrometer, an omegatron or the like. Further,preferably an atmospheric pressure ionization mass spectrometer is used.Atmospheric pressure ionization mass spectrometry (APIMS, AtmosphericPressure Ionization Mass Spectrum) which depends on an atmosphericpressure ionization method (API, Atmospheric Pressure Ionization) ismeans which can analyze minute quantities of impurities, and has aspecial feature in the point that it can carry out measurements withhigh sensitivity in real time. This is due to the fact that the gasintroduction portion of APIMS can be operated at atmospheric pressure.In order to plan the making of high sensitivity with a massspectrometer, it is necessary to increase the amount of ionization (highefficiency ionization) of the detection object component, but in APIMShigh efficiency ionization is achieved by two-step ionization. First, inthe beginning a sample gas (main component: C, impurity: X) containing aminute quantity of impurity undergoes primary ionization by coronadischarge in an ionization portion. In the primary ionization, only oneportion of the sample is ionized in the same way as in many ionizationmethods. The composition of the created ions is roughly the same as thesample, and is formed by the main component ion C⁺ which is the majorportion and a slight amount of the impurity ion X⁺. In an electronimpact ionization method (EI) which is carried out under normal reducedpressure, because the ions created by only one-step ionizationcorresponding to this primary ionization are detected, the amount of theobject impurity ion X⁺ is small, and this makes it difficult to carryout high sensitivity detection. On the other hand, in the atmosphericpressure ionization method, an increase of X⁺ is planned using thefollowing secondary ionization. Namely, C⁺ from the ions created by theprimary ionization are useless ions for the purpose of analysis. Theseuseless ions C⁺ search out most of the remaining impurities X which havenot been ionized yet, and this is a method of moving charges bycharge-exchange reactions. These ion molecular reactions are reactionswhich move charges from a high ionization potential to a low ionizationpotential. Because the carrier gas (nitrogen, argon, hydrogen or thelike) has a higher ionization potential than the impurity molecules(H₂O, O₂, organic matter and the like), it becomes possible to carry outhigh sensitivity analysis of impurities.

APIMS is less affected even when a large amount of carrier gas such asargon or nitrogen gas is flowed. Accordingly, gas remnants inside theplastic container are controlled by flowing a large amount of carriergas, and it is possible to carry the permeated measurement object gasdirectly to the detector. In this way, the response speed of detectioncan be made higher, and this makes it possible to carry out detection inroughly real time. In addition, it is possible to shorten the waitingtime until the gas concentration inside the container reaches a steadystate. Further, because the concentration (partial pressure) of thepermeated measurement object gas is inevitably lowered if there is alarge amount of carrier gas, a detection method which can carry outminute quantity analysis is required. For the reason given above, therehas been a demand for a method which can carry out minute quantityanalysis and does not lower the detection accuracy even when a largeamount of carrier gas is flowed as in APIMS.

As described above, by combining heat drying with the use of anatmospheric pressure ionization analyzer, the gas barrier property ofthe plastic molded body when first used as a container can be measuredat high accuracy and high speed.

In the oxygen barrier property measuring apparatus represented by theOX-TRANTWIN manufactured by Modern Control Company shown in JapaneseLaid-Open Patent Application No. HEI 8-53116, the measurement accuracyis lowered when a large amount of carrier gas is flowed. The carrier gasflow rate can be up to a maximum of 50 ml/min, and most measurements areat about 10 ml/min. On the other hand, in the measuring method accordingto the present embodiment, in the atmosphere adjusting process and themeasurement object gas measuring process, the flow rate per one minuteof argon gas supplied to the argon atmosphere side is preferably greaterthan or equal to twice the volume of the plastic container, for example,the carrier gas flow rate in a 350 ml container can be made a maximum of2000 ml/min, and measurements are carried out at about 500˜1000 ml/min.In this way, compared with the measuring method used in

Japanese Laid-Open Patent Application No. HEI 8-53116, in the measuringmethod according to the present embodiment, because it is possible toflow 50˜100 times as much carrier gas (purge gas), a steady state can bereached quickly. In particular, it is possible to control gas remnantsinside the container and carry out gas substitution quickly at the timethe gas barrier property of a plastic container having a complicatedthree-dimensional shape inside is evaluated. Even in the above-describedoxygen barrier property measuring apparatus disclosed in JapaneseLaid-Open Patent Application No. HEI 8-53116, it is possible toeliminate the effects of water and quickly reach a steady state byproviding a heat drying process.

Further, because the gas permeability coefficient inside plastic has atemperature dependency and a humidity dependency, measurements need tobe carried out at a constant temperature.

For example, as shown in FIG. 1 and FIG. 2, the method of measuring agas barrier property of a plastic molded body according to the presentinvention can be applied to gas barrier property plastic containerswhich are manufactured by a mass production machine in which a pluralityof coating chambers are arranged for coating a gas barrier property thinfilm on one of the inner surface or the outer surface of the plasticcontainers or on both thereof and coating is carried out in a massproduction manner by simultaneously or sequentially operating saidcoating chambers. Namely, a heat drying process, an atmosphere adjustingprocess and a measurement object gas measuring process are carried outat a level where a prescribed number of film formations is carried outin each coating chamber, and then a chamber operation judgment processwhich judges poor operation of the coating chambers by comparing the gasbarrier property of the gas barrier property plastic containers in eachcoating chamber is carried out.

FIG. 1 is a conceptual drawing showing the structure of a coatingapparatus in which a plurality of coating chambers (film formationchambers) is arranged in the shape of a circle, and a gas barrier thinfilm is coated on one of the inner surface or the outer surface of thecontainer or on both surfaces thereof during the period in which thecircle is rotated once. FIG. 2 is a conceptual drawing showing thearrangement of coating chambers and each corresponding process in therotating apparatus. Further, the letters A, B assigned to the coatingchambers show the type of high frequency power source, wherein the highfrequency power source A (not shown in the drawings) and the highfrequency power source B (not shown in the drawings) supply a highfrequency to the sequential coating chambers.

In this regard, a heat drying process, an atmosphere adjusting processand a measurement object gas measuring process are carried out at alevel where a prescribed number of film formations is carried out ineach coating chamber. Observations are carried for one specific coatingchamber arranged in the circle. For example, the film formationapparatus of FIG. 1 forms a gas barrier property thin film every timethe circle undergoes one rotation, and a plastic container that hasundergone film formation is sampled at every 100 film formations (everytime the circle undergoes 100 rotations), and the gas barrier propertyof said plastic container is measured by the measuring method accordingto the present embodiment described above. This is also carried out inthe same way for the other coating chambers. The sampling proportion isappropriately determined in accordance with the manufacturing rate ofthe mass production machine. Next, the gas barrier properties of the gasbarrier property plastic containers in each coating chamber arecompared. When there is a container having a low gas barrier propertycompared with the average value of the gas barrier property of eachcontainer, the coating chamber corresponding to said container isassumed to have poor operation, and so the coating chamber is judged tohave poor operation. In this kind of case, because there is a strongpossibility that the gas barrier property thin film coated plasticcontainer that underwent film formation in the poor operation coatingchamber has a poor quality gas barrier property, quality confirmationsuch as the carrying out of a separate gas barrier measurement may becarried out by sampling from mass produced gas barrier property thinfilm coated plastic containers. Further, as long as there is a judgmentof the quality of the operation of each coating chamber, measurements ofthe amount of gas permeation may be carried out before the amount of gaspermeation completely stabilizes, and in this case, preferably themeasurement conditions are standardized.

Next, before describing the specific gas barrier property measuringmethod of the present embodiment, a description will be given for anembodiment of a gas barrier property measuring apparatus for carryingout the present measuring method. This apparatus is shown for thepurpose of describing the measuring method, and the measuring method isnot limited to this apparatus structure.

FIG. 3 shows a schematic drawing showing one embodiment of a plasticcontainer gas barrier property measuring apparatus. The pipelinestructure of the present apparatus is a measurement object gas detectingstructure constructed from a liquid argon tank 1, a liquid argonvaporizer 2, a pressure reducing valve 3 and a getter 4 (GT100,manufactured by Nihon API Company) which removes impurities such aswater molecules and the like connected in that order by a pipeline, anda bypass line 5 and a PET bottle (PET bottle) line 8 provided to branchin parallel downstream of the getter 4, a repurifier (MS-10J,manufactured by Nihon API Company) through which impurities pass and areremoved after the bypass line 5 and the PET bottle line 8 flow togetheragain, and an APIMS 15 (UG-240PN manufactured by Hitachi TokyoElectronics Company).

A mass flow controller 6 and a purifier 7 are connected in that order bya pipeline to the bypass line 5, and a mass flow controller 9, apurifier 10, the inside space of a PET bottle 11, a valve B 11 and avalve A 13 are connected in that order by a pipeline to the PET bottleline 8. In the PET bottle 11, a gas supply pipeline 16 and a gas exhaustpipeline 17 are inserted in the mouth portion so that gas is introducedfrom the mouth portion and gas is exhausted from the mouth portionrepeatedly.

Further, PET bottle outside atmosphere adjusting means 31 connected by apipeline sequentially to a standard gas cylinder 21 (e.g., Ar (99%)-H₂(1%)), a pressure reducing valve 22, a mass flow controller 23 and PETbottle sealing means 24 such as a bag made of polypropylene are preparedin order to adjust the atmosphere outside the PET bottle (PET bottle)11.

In the PET bottle sealing means 24 such as a bag made of polypropylene,when the PET bottle is covered and the PET bottle outside atmosphereadjusting means 31 is operated to make the atmosphere outside the PETbottle become Ar (99%)-H₂ (1%), for example, hydrogen which is themeasurement object gas permeates from the outer surface of the PETbottle to the inner surface by diffuse permeation. Further, the hydrogenthat has permeated to the inside of the plastic container is carried tothe outside of the container by argon flowing through the PET bottleline 8 as a carrier gas, and the hydrogen concentration inside the argonis detected using the APIMS 15.

The means which heats the plastic molded body in the heat drying processcan be illustrated by an apparatus (not shown in the drawings) in whichthe molded body is inserted in a heating chamber and blown with hot gas,an apparatus (not shown in the drawings) in which the plastic moldedbody is wound with a heater and wrapped by a heat conducting body suchas aluminum foil or the like to heat the entire molded body or the like.Any apparatus may be used so long as it is possible to carry out overallheating at a level which does not cause heat deterioration ordeformation of the plastic molded body.

With the apparatus shown in FIG. 3 forming a base, a description will begiven for the operating procedure of the gas barrier property measuringmethod according to the present embodiment.

(1) Background Measurement

In the mass flow controller 6, argon gas is flowed (flowed to the bypassline 5) at 1 liter/minute and background data is measured. At this time,the valve A 13 is closed.

(2) Baking of the PET Bottle

The baking of the PET bottle 11 is carried out during the period of (1).For example, the entire container is heated by being wrapped by a heatconducting body such as aluminum foil or the like. In the mass flowcontroller 9, argon gas is flowed at 1 liter/minute in the PET bottle11, and baking is carried out for 30 minutes at 80° C. in the case of aheat resistant PET bottle. At this time, the valve B 12 is opened andgas is exhausted. Further, when flowing gas to the PET bottle 11, eitherthe valve A 13 or the valve B 12 must be open. Further, as was describedin the operation column, heat drying is carried out at or below atemperature level where shape deterioration and thin film deteriorationsuch as peeling, cracking and like of the gas barrier property thin filmdo not occur, and preferably drying is carried out while blowing hot gassuch as dry nitrogen gas, dry argon gas or the like in the container.

(3) Analysis of PET Bottle Line (Room Atmosphere)

In order to complete the heat drying process, the heater and thealuminum foil attached to the PET bottle 11 are removed. The valve B 12is closed, the valve A 13 is opened, and the gas of the mass flowcontroller 6 (bypass line 5) is stopped to begin analysis of the PETbottle line 8. At this time, the PET bottle is surrounded by air (roomatmosphere), and in this state, analysis is carried out for a prescribedperiod of time such as 1 hour, for example.

(4) Analysis of PET Bottle Line (Standard Gas: Ar (99%)-H₂ (1%)Atmosphere)

The PET bottle 11 covered with a polypropylene bag 24, Ar (99%)-H₂ (1%)is flowed at 500 cc/minute in the mass flow controller 23, and analysisis carried out for a prescribed period of time such as 1 hour, forexample.

The description given above was for the purpose of describing themeasuring method, and the combination shown in Table 1 may be used as astandard gas.

SPECIFIC EXAMPLES Specific Example 1

In the specific examples, a heat resistant round type PET bottle havinga height of 157 mm, a trunk diameter of 68 mm, a mouth diameter of 28mm, a thickness of 0.35 mm, a volume of 350 ml and a surface area of 320cm formed a container for measurement. An apparatus which includes thegas system shown in FIG. 3 was used as a measuring apparatus. An APIMS(UG-240PN manufactured by Hitachi Tokyo Electronics Company) was used asa measurement object gas detector. Measurements were carried out inaccordance with the operating procedures (1), (2) and (3) of the gasbarrier property measuring method according to the present embodiment.The time when the atmosphere outside the container formed the roomatmosphere (air atmosphere) formed Specific Example 1.

Specific Example 2

Continuous with Specific Example 1, the operating procedure (4) of thegas barrier property measuring method of the present embodiment wascarried out, and the time when the atmosphere outside the containerformed the standard gas: Ar (99%)-H₂ (1%) atmosphere formed SpecificExample 2.

In Specific Examples 1 and 2, the changes in oxygen concentration andhydrogen concentration depending on the measurement elapsed time areshown in FIG. 4. Further, the relationship between the ionic strengthand the mass number at the time of the background measurement of theoperating procedure (1) of the gas barrier property measuring method isshown in FIG. 5. The relationship between the ionic strength and themass number at the time of the oxygen concentration measurement ofSpecific Example 1 is shown in FIG. 6. The relationship between theionic strength and the mass number at the time of the hydrogenconcentration measurement of Specific Example 2 is shown in FIG. 7.

Specific Examples 3 and 4

A measurement object container was formed by a heat resistant round typePET bottle the same as that in Specific Example 1 in which a DLC filmhaving a thickness of 9 nm was formed (at a film formation time of 0.9seconds) uniformly on the inner surface. At this time, the output of thehigh frequency power supplied for film formation in a high frequencyplasma CVD apparatus which was the same as that in Japanese Laid-OpenPatent Application No. HEI 8-53116 was made 500 W. Measurements werecarried out in the same way as in Specific Examples 1 and 2, wherein thetime when the atmosphere outside the container formed the roomatmosphere (air atmosphere) formed Specific Example 3 and the time whenthe atmosphere outside the container formed the standard gas: Ar(99%)-H₂ (1%) atmosphere formed Specific Example 4.

In Specific Examples 3 and 4, the changes in oxygen concentration andhydrogen concentration depending on the measurement elapsed time areshown in FIG. 8. Further, the relationship between the ionic strengthand the mass number at the time of the background measurement of theoperating procedure (1) of the gas barrier property measuring method isshown in FIG. 9. The relationship between the ionic strength and themass number at the time of the oxygen concentration measurement ofSpecific Example 3 is shown in FIG. 10. The relationship between theionic strength and the mass number at the time of the hydrogenconcentration measurement of Specific Example 4 is shown in FIG. 11.

Specific Examples 5 and 6

A measurement object container was formed by a heat resistant round typePET bottle the same as that in Specific Example 1 in which a DLC filmhaving a thickness of 14 nm was formed (at a film formation time of 1.4seconds) uniformly on the inner surface. The film formation conditionswere the same as in the case of Specific Examples 3 and 4. Measurementswere carried out in the same way as in Specific Examples 1 and 2,wherein the time when the atmosphere outside the container formed theroom atmosphere (air atmosphere) formed Specific Example 5 and the timewhen the atmosphere outside the container formed the standard gas: Ar(99%)-H₂ (1%) atmosphere formed Specific Example 6.

Specific Examples 7 and 8

A measurement object container was formed by a heat resistant round typePET bottle the same as that in Specific Example 1 in which a DLC filmhaving a thickness of 19 nm was formed (at a film formation time of 1.9seconds) uniformly on the inner surface. The film formation conditionswere the same as in the case of Specific Examples 3 and 4. Measurementswere carried out in the same way as in Specific Examples 1 and 2,wherein the time when the atmosphere outside the container formed theroom atmosphere (air atmosphere) formed Specific Example 7 and the timewhen the atmosphere outside the container formed the standard gas: Ar(99%)-H₂ (1%) atmosphere formed Specific Example 8.

Specific Examples 9 and 10

A measurement object container was formed by a heat resistant round typePET bottle the same as that in Specific Example 1 in which a DLC filmhaving a thickness of 24 nm was formed (at a film formation time of 2.4seconds) uniformly on the inner surface. The film formation conditionswere the same as in the case of Specific Examples 3 and 4. Measurementswere carried out in the same way as in Specific Examples 1 and 2,wherein the time when the atmosphere outside the container formed theatmosphere (air atmosphere) inside the chamber formed Specific Example 9and the time when the atmosphere outside the container formed thestandard gas: Ar (99%)-H₂ (1%) atmosphere formed Specific Example 10.

The measured results of the amount of permeation of oxygen and hydrogenin Specific Examples 1˜10 are shown in Table 3.

After the amount of permeation stabilized, the amount (ng) of permeationin 13 minutes is determined. This determined value is calculated basedon the amount (cc/day/pkg) of permeation per one of each container.Further, the relationship between the film thickness of the DLC film andthe amount of oxygen permeation is shown in FIG. 12, and therelationship between the film thickness of the DLC film and the amountof hydrogen permeation is shown in FIG. 13. Further, pkg is anabbreviation of Package. TABLE 3 Amount of Oxygen Permeation Amount ofHydrogen Permeation Amount of Amount of Amount of Permeation per Amountof Permeation per Permeation in each 1 container Permeation in each 1container Sample 13 minutes (ng) (cc/day/pkg) 13 minutes (ng)(cc/day/pkg) Specific 701 0.0544 36.17 0.0449 Example 1, 2 Specific400.1 0.0310 30.16 0.0374 Example 3, 4 Specific 222.53 0.0173 24.120.0299 Example 5, 6 Specific 218.41 0.0169 17.29 0.0215 Example 7, 8Specific 191.87 0.0149 15.92 0.0198 Example 9, 10

As is understood from the results of Table 3, FIG. 12 and FIG. 13, it isclear that there is a relationship in which the amount of gas permeationbecomes lower as the film thickness is made larger, and it was possibleto evaluate the oxygen barrier property and the hydrogen barrierproperty. At this time, referring to FIG. 4 as an example, it tookapproximately 1.5 hours from the heat drying process to the completionof the oxygen barrier property measurement, and the total measurementtime continued up to the completion of the hydrogen barrier propertymeasurement was 2.5 hours, whereby it was possible to carry outmeasurements in a very short period of time. In Specific Examples 1˜10,as is clear with reference to FIG. 4 or FIG. 8, for example, it ispossible to measure the amount of oxygen gas permeation or the amount ofhydrogen gas permeation in about 1.5 hours, and in the case wheremeasurements of the amount of oxygen gas permeation and the amount ofhydrogen gas permeation are continued, because the heat drying processcan be omitted one time, evaluation can be carried out in 2.5 hours.

In Specific Examples 1˜10, a method of measuring oxygen gas and hydrogengas was shown, but by adjusting the atmosphere outside the containerusing a standard gas shown in Table 1, it is possible to carry outmeasurements in a short period of time in the same way as in thespecific examples for the amount of gas permeation of carbon dioxide gasand oxygen gas (mass number 18).

Specific Example 11 and Comparative Example 1

A comparison of the times required until the oxygen concentrationstabilized was carried out by examining the change in oxygenconcentration inside the carrier gas flowing through the inside of a PETcontainer in the case where drying by heat drying was carried out andthe case where it is not carried out. PET containers are containerswhich have a high hygroscopicity. Evaluation was carried out using thesame containers as in Specific Example 1. The case where a plasticcontainer underwent heat drying at 55° C. for 3 hours formed SpecificExample 11, and the case where heat drying was not carried out formedComparative Example 1. Further, in Specific Example 11, argon gas wasflowed through the inside of the container at a flow rate of 1000ml/minute during heat drying. The outside of the container formed an airatmosphere. The results are shown in FIG. 15. FIG. 15 is a graph showingthe change in oxygen concentration inside the carrier gas flowingthrough the inside of the PET container, and at the case where there isa heat drying process and the case where there is none. As is clear withreference to FIG. 15, in Specific Example 11, from the time measurementsare begun (the time where 4 hours have elapsed in the drawing), theoxygen concentration is fixed at roughly 40 ppb, and after the heatdrying process, it is possible to immediately carry out evaluation ofthe oxygen permeability. On the other hand, in Comparative Example 1,the oxygen concentration is lowered gradually as time elapses, and theoxygen concentration finally reaches roughly 40 ppb at the time when 38hours have elapsed in the drawing. Accordingly, the time required untilthe beginning of measurements is clearly short in Specific Example 11which undergoes a heat drying process. Accordingly, the effect of havinga heat drying process became clear.

Specific Example 12 and Comparative Example 2

A comparison of the times required until the oxygen concentrationstabilized was carried out by examining the change in oxygenconcentration inside the carrier gas flowing through the inside of apolyethylene container in the case where drying by heat drying wascarried out and the case where it is not carried out. Polyethylenecontainers are containers which have a low hygroscopicity. Evaluationwas carried out with containers having the same size as the containersin Specific Example 1. The case where a plastic container underwent heatdrying at 70° C. for 20 minutes formed Specific Example 12, and the casewhere heat drying was not carried out formed Comparative Example 2.Further, in Specific Example 12, argon gas was flowed through the insideof the container at a flow rate of 1000 ml/minute during heat drying.The outside of the container formed an air atmosphere. The results areshown in FIG. 16. FIG. 16 is a graph showing the change in oxygenconcentration inside the carrier gas flowing through the inside of thepolyethylene container, and at the case where there is a heat dryingprocess and the case where there is none. With reference to FIG. 16, inSpecific Example 12, the oxygen concentration is lowered gradually astime elapses from the time measurements are begun (the time where 26minutes have elapsed in the drawing). On the other hand, in ComparativeExample 2, the oxygen concentration is lowered gradually as time elapsesfrom the time measurements are begun (the time where 6 minutes haveelapsed in the drawing). However, in Specific Example 12, the oxygenconcentration is lower than even Comparative Example 10, and the oxygenpermeability stabilizes quickly. Accordingly, even in a polyethylenecontainer which is a container having a low hygroscopicity, it ispossible to shorten the time required until measurements are begun byproviding a heat drying process. Accordingly, the effect of having aheat drying process became clear.

Comparative Example 3

A heat resistant round type PET bottle (non-coated bottle) which was thesame as that in Specific Example 1 formed the measurement container.Instead of carrying out the heat drying process of the operatingprocedure (2) of the gas barrier property according to the presentembodiment, oxygen concentration measurements were carried out afterargon was flowed at a flow rate of 1 liter/minute for 10 hours withoutheating, and this formed Comparative Example 3.

In Comparative Example 3, the values finally stabilized after argon wasflowed at 1000 cc/minute for 10 hours. Compared with Specific Example 1,a long time was required for drying to remove water molecules, and quickmeasurements were impossible.

Comparative Examples 4, 5, 6, 7 and 8

Using an OX-TRAN2/21 manufactured by Mocon Company, measurements of theamount of oxygen permeation (cc/day/pkg) were carried out for thenon-coated plastic container measured in Specific Examples 1 and 2, thecoated plastic container that underwent film formation for 0.9 secondsmeasured in Specific Examples 3 and 4, the coated plastic container thatunderwent film formation for 1.4 seconds measured in Specific Examples 5and 6, the coated plastic container that underwent film formation for1.9 seconds measured in Specific Examples 7 and 8, and the coatedplastic containers that underwent film formation for 2.4 secondsmeasured in Specific Examples 9 and 10 with the inside of the containersat 23° C.-55% RH, the outside of the containers at 23° C.-100% RH, andthe oxygen partial pressure at 21%. These sequentially formedComparative Example 4, Comparative Example 5, Comparative Example 6,Comparative Example 7 and Comparative Example 8 as shown in Table 4. Asfor the measurement times, measurements were carried out after 1 day,after 2 days, after 3 days, after 4 days, after 5 days and after 6 days,respectively. These results are shown in Table 5. TABLE 4 Film FormationDLC Film Sample Time (seconds) Thickness (nm) Comparative Example 4 0 0Comparative Example 5 0.9 9 Comparative Example 6 1.4 14 ComparativeExample 7 1.9 19 Comparative Example 8 2.4 24

TABLE 5 Day Number Sample 1 2 3 4 5 6 Comparative 0.0324 0.0265 0.02510.0247 0.0239 0.0244 Example 4 Comparative 0.0142 0.0123 0.0113 0.01130.0107 0.0107 Example 5 Comparative 0.0077 0.0068 0.0060 0.0057 0.00540.0055 Example 6 Comparative 0.0062 0.0056 0.0054 0.0053 0.0051 0.0052Example 7 Comparative 0.0050 0.0043 0.0042 0.0040 0.0040 0.0040 Example8Units: Amount of permeation per each 1 container (cc/day/pkg)

The relationship between the measurement elapsed time and the amount ofoxygen permeation in Comparative Examples 4˜8 is shown in FIG. 14.

In Comparative Examples 4˜8, there is no provision of a heat dryingprocess, and it is not possible to flow a large amount of argon gas as acarrier gas. At this time, a long period of time is required until themeasurement data stabilizes. During this long period of time, it isassumed that water molecules are removed, and the inside of thecontainer undergoes gas substitution. As is clear with reference to FIG.14, approximately 5˜6 days was required until the amount of oxygenpermeation stabilized. It was understood that the evaluation time wasvery long compared with the fact that it was possible to completemeasurements of the amount of oxygen permeation in 1.5 hours after thebeginning of measurements in Specific Examples 1, 3, 5, 7 and 9.

1. A method of measuring the gas barrier property of a plastic moldedbody comprising drying the plastic molded body with a heat dryingprocess which heats and dries said plastic molded body in a temperaturerange which does not cause deformation or heat deterioration; andmeasuring the amount of permeation of a measurement object gaspermeating through the plastic molded body with a gas analyzer.
 2. Themethod of measuring the gas barrier property of a plastic molded body ofclaim 1, further comprising an atmosphere adjusting process comprisingforming an atmosphere comprising a measurement object gas at one side ofthe wall surfaces of said plastic molded body, and forming a carrier gasatmosphere which carries said measurement object gas after permeation tosaid gas analyzer at the other side, thereby forming a front and backrelationship of said wall surfaces.
 3. The method of measuring the gasbarrier property of a plastic molded body of claim 2, wherein saidcarrier gas atmosphere is an argon atmosphere or a nitrogen gasatmosphere.
 4. The method of measuring the gas barrier property of aplastic molded body of claim 2, wherein the heat drying process iscarried out at the same time as the atmosphere adjusting process.
 5. Themethod of measuring the gas barrier property of a plastic molded body ofclaim 3, further comprising a measurement object gas measuring processwhich measures the amount of permeation of said measurement object gaspermeating through said plastic molded body from one side of said wallsurfaces toward the other side with said gas analyzer at the time whensaid amount of permeation of said measurement object gas reaches aroughly steady state.
 6. The method of measuring the gas barrierproperty of a plastic molded body of claim 1, wherein said heat dryingprocess comprises a process which removes water absorbed by said plasticmolded body.
 7. The method of measuring the gas barrier property of aplastic molded body of claim 2, wherein said heat drying processcomprises a process which substitutes an adsorption gas adsorbed on oneside of the wall surfaces of said plastic molded body with gas of theatmosphere comprising said measurement object gas, and substitutes theadsorption gas adsorbed on the other side, thereby forming a front andback relationship of the wall surfaces of said plastic molded body withthe gas of said carrier gas atmosphere.
 8. The method of measuring thegas barrier property of a plastic molded body of claim 1, wherein saidgas analyzer is a mass spectrometer.
 9. The method of measuring the gasbarrier property of a plastic molded body of claim 8, wherein said massspectrometer is an atmospheric pressure ionization mass spectrometer(APIMS).
 10. The method of measuring the gas barrier property of aplastic molded body of claim 2, wherein said plastic molded body is aplastic container or a gas barrier property plastic container in which agas barrier property thin film is coated on one of the inner surface,the outer surface, or both surfaces thereof, and the atmospherecomprising a measurement object gas is formed outside the container andsaid carrier gas atmosphere is formed inside the container in saidatmosphere adjusting process.
 11. The method of measuring the gasbarrier property of a plastic molded body of claim 2, wherein saidmeasurement object gas is oxygen gas, and the atmosphere including saidmeasurement object gas is an air atmosphere.
 12. The method of measuringthe gas barrier property of a plastic molded body of claim 2, whereinsaid measurement object gas is oxygen gas, carbon dioxide gas, hydrogengas, or a combination thereof, and the atmosphere comprising saidmeasurement object gas is a measurement object gas-argon atmosphere or ameasurement object gas-nitrogen gas atmosphere in which adjustments arecarried out so that said measurement object gas forms a prescribedpartial pressure.
 13. The method of measuring the gas barrier propertyof a plastic molded body of claim 2, wherein said measurement object gasis oxygen gas of mass number 18, and the atmosphere comprising saidmeasurement object gas is an oxygen gas of mass number 18-argonatmosphere or an oxygen gas of mass number 18-nitrogen gas atmosphere inwhich adjustments are carried out so the oxygen gas of mass number 18forms a prescribed partial pressure.
 14. The method of measuring the gasbarrier property of a plastic molded body of claim 2, wherein saidmeasurement object gas is a mixed gas of oxygen gas of mass number 18and at least one gas from oxygen gas of mass number 16, carbon dioxidegas or hydrogen gas, and the atmosphere including said measurementobject gas is a measurement object gas-argon atmosphere or a measurementobject gas-nitrogen gas atmosphere in which adjustments are carried outso that said measurement object gas forms a prescribed partial pressure.15. The method of measuring the gas barrier property of a plastic moldedbody of claim 5, wherein said plastic molded body is a gas barrierproperty plastic container which is mass produced by arranging aplurality of coating chambers for coating the inner surface or the outersurface of the plastic container or both surfaces thereof with a gasbarrier property thin film and operating said coating chamberssimultaneously or sequentially, said heat drying process, saidatmosphere adjusting process and said measurement object gas measuringprocess are carried out at a level where a prescribed number of filmformations is carried out in each of said coating chambers, and then achamber operation judgment process which judges poor operation of saidcoating chambers by comparing the gas barrier properties of said gasbarrier property plastic containers in each of said coating chambers iscarried out.
 16. The method of measuring the gas barrier property of aplastic molded body of claim 5, wherein the argon flow rate per 1 minuteor the nitrogen flow rate per 1 minute supplied to said carrier gasatmosphere side is greater than or equal to twice the volume of saidplastic container in said atmosphere adjusting process and saidmeasurement object gas measuring process.